Shaft seal



July 16, 1957 E. c. KING ET AL 2,799,522

SHAFT SEAL Filed Jan. 7, 1954 Earle C. King Ver'ne K. Heckel INVENTORSwgw their AHorney United States Patent SHAFT SEAL Earle C. King, EvansCity, and Verne K. Heckel, Prospect, Pa., assignors to Mine SafetyAppliances Company, Pittsburgh, Pa. a corporation of PennsylvaniaApplication January 7, 1954, Serial No. 402,674

8 Claims. (Cl. 286-1) This invention relates to new and usefulimprovements in seals for shafts and more particularly to a seal for arotating shaft which extends into a container holding a molten metalunder pressure.

One of the objects of this invention is to provide a new and improvedseal for a shaft extending into a container filled with a moltenmaterial.

Another object of this invention is to provide a new and improved sealfor a rotating shaft extending into a container filled with moltenmaterial which comprises freezing a substantial amount of the moltenmaterial around the shaft toprovide a liquid type seal.

Another object of this invention is to provide a seal for a rotatableshaft extending into the container filled with a molten material whichcomprises a mass of metal wool packed around said shaft and providedwith a cooling means operable to freeze the molten material which entersthe space filled with said metal wool packing.

Other objects will become apparent from time to time throughout thespecification and claims as hereinafter related.

This invention comprises the new and improved construction andcombination of parts and their relation one to another which will bedescribed more fully hereinafter and the novelty of which will beparticularly pointed out and distinctly claimed.

In the accompanying drawings, to be taken as a part of thisspecification, there are clearly and fully illustrated two preferredembodiments of this invention, in which drawings:

Figure 1 is a diagrammatic view of a container such as a pump housingand showing in longitudinal section the shaft seal which comprises thisinvention, and

Figure 2 is a detailed sectional view of another embodiment of the shaftseal disclosed in Figure 1.

Referring to the drawings by numerals of reference and more particularlyto Fig. 1 there is shown diagrammatically a container 1 which may be apump or a reaction vessel or any other container for molten materialssuch as molten metals. The container 1 is shown as having an inlet 2 andan opening 3 in the side wall thereof. The opening 3 has a metal sleeve4 extending outward therefrom. The container 1 also has an outlet 5therefrom. A shaft 6 extends into the container 1 concentrically throughthe sleeve 4 and the opening 3. The shaft 6 may be the shaft for a pumpor for a stirrer or a valve or any other apparatus having a reciprocableor rotatable shaft. The sleeve 4 is provided with an annular retainingring 7 adjacent the inner end portion thereof. The space between thesleeve 4 and the shaft 6 is tightly packed with a metal wool packing 8which for most liquid metals is preferably a stainless steel wool. Thesteel wool adjacent the inner end of the sleeve 4 is wrapped with wire 8to provide aseal against steel wool working into the container. At theouter open end of the sleeve 4 there is provided a non-metallic packing9, which for most installations is an asbestos type packing. Thenon-metallic packing 9 is packed tightly into them- 2,799,522 PatentedJuly 16,- 1957 ice nular space at the open end of the sleeve 4 and isoperable to pack the metal wool packing 8 tightly against the annularretaining ring 7. The non-metallic packing 9 is held in place by a capmember 10 which is secured on the sleeve 4 as by a threaded connection11. The cap member 10 is provided with a central aperture 12 throughwhich extends the shaft 6. The sleeve 4 is provided with a suitablecooling means surrounding the portion which is filled with the metalwool packing. The sleeve 4 is also provided with an oil filler tube 17for lubricating the packing. In this embodiment of the invention thecooling means is a metal coil 13 which is wrapped tightly around thesleeve 4 and which may if desired, be soldered or otherwise connected tothe sleeve 4 for more eflicient heat transfer. The cooling coil 13 hasinlet and outlet connections 14 and 15 for circulation of a coolingfluid through the coil.

The operation of this apparatus is relatively simple but should beconsidered carefully in view of certain prior art attempts to solve thisproblem. The container 1 and inner end portion of the sleeve 4 arefilled with a molten material 16 which may be a liquid metal such assodium, potassium, or a low melting point sodium-potassium alloy, orother metals or alloys having a relatively low melting point. Some ofthe molten material 16 will pass through the clearance between theretaining ring 7 and the shaft 6 and will enter the annular space whichis filled with the metal wool packing 8. The molten material whichenters this space will be frozen immediately into a solid mass by thecoolant which passes through the cooling coil 13. The heat transfercapacity of the cooling coil 13 is, of course, designed to freeze themolten material and form a seal for the shaft in a relatively shortdistance from the retaining ring 7. If at any time this frozen seal isbroken and moltenmaterial allowed to flow past it such a break will beimmediately sealed by the molten material freezing at a point outwardfrom the break.

it should be noted that there have been other proposals to providefrozen seals from molten materials which are similar to the one which wepropose here but which do not make use of the metal wool packing whichwe propose. We have found experimentally that seals which do not use themetal wool packing cause an excessi e binding on the shaft and make itvery difiicult, if not impossible, to start rotation of the shaft afterit has been stopped for any substantial period of time. We have foundhowever that the incorporation of a metal wool packing into this type ofseal provides a seal which is more efficient than one which does notcontain this packing and also will permit the shaft to be rotated easilyeven after it has been stopped for an extended period of time. As anexample we have found that with a pump using liquid sodium and a frozenseal of this general type but without the metal wool packing, when thepump was stopped for a short time the shaft could not be turned usingthe powerful leverage of an extension wrench. In a similar pump whichused our seal including the metal wool packing we found that even afterstopping the pump for an extended period of time it was possible to turnthe shaft by hand.

in Figure 2 there is shown another form of this invention in which thesleeve is provided with heat transfer fins for cooling the packingsufliciently to freeze the metal and provide the desired seal. In thisfigure corresponding parts are given the same reference numerals as inFig. 1 and the fins are given the reference numeral 18. The operation ofthis embodiment of the invention is identical with that disclosed inconnection with Fig. 1.

Although we have described and disclosed only two embodiments of thisinvention it will be obvious to those skilled in the art that otherembodiments of this invention can be made without departing from thescope and intent of this invention which should be limited only by theappended claims.

Having thus described our invention, what we desire to claim and secureby Letters Patent is:

l. The combination with a container substantially filled with a moltenmaterial, of a sleeve extending outward from the container, a movableshaft extending from within said container outward through said sleeve,a metal Wool packing surrounding said shaft within said sleeve, andcooling means surrounding said sleeve and operable to freeze any of saidmolten material entering the space filled with said metal wool packing.

2. An apparatus as defined in claim 1 in which said shaft is rotatable.

3. An apparatus as defined in claim 1 in which said shaft isreciprocable.

4. An apparatus as defined in claim 1 in which said cooling meanscomprises a fluid conducting heat exchange conduit extending around saidsleeve.

5. An apparatus as defined in claim 1 in which said cooling meanscomprises heat dissipating fins on said sleeve.

6. The combination with a container having an opening and filled withmolten metal under pressure, of a metal sleeve extending outward fromsaid opening, a movable shaft extending concentrically through saidopening and said sleeve, an annular retaining member in the end of saidsleeve adjacent said opening, a metal wool packing surrounding saidshaft within said sleeve, a nonmetallic packing surrounding said shaftadjacent the outer end of said sleeve, a cap member closing the outerend of said sleeve and urging said nonmetallic packing compressivelyagainst said metal wool packing to compress the same against saidannular member, said cap member having an aperture through which saidshaft extends, and a metal heat transfer conduit coiled around saidsleeve in contact therewith and operable to conduct a cooling fluid forcooling said sleeve sufiiciently to freeze any molten metal which entersthe space filled with said metal wool packing.

7. The combination with a container having an opening and filled withmolten metal under pressure, of a metal sleeve extending outward fromsaid opening, a movable shaft extending concentrically through saidopening and said sleeve, an annular retaining member in the end of saidsleeve adjacent said opening, a metal wool packing surrounding saidshaft within said sleeve, a nonmetallic packing surrounding said shaftadjacent the outer end of said sleeve, a cap member closing the outerend of said sleeve and urging said nonmetallic packing compressivelyagainst said metal wool packing to compress the same against saidannular member, said cap member having an aperture through which saidshaft extends, and heat transfer fins on said sleeve and operabie toconduct heat away from said sleeve at a rate sufiicient to freeze anymolten metal which enters the space filled with said metal Wool packing.

8. An apparatus as defined in claim 1 in which there is provided anon-metallic packing positioned in the outer end portion of said sleeveto hold said metal wool packing packed tightly in position, and a capmember closing the outer end portion of said sleeve to hold saidnonmetallic packing in position and provided with an aperture throughwhich said shaft extends.

References Cited in the file of this patent UNITED STATES PATENTS

